The development of a sound scientific data base that includes key information in the areas of neutronics, thermophysical properties, and materials for cyclic gaseous core reactors has been the objective of a lengthy theoretical/experimental research program at the University of Florida. The most recently completed phase of this program includes theoretical neutronics modeling and experimental verification. Static and dynamic neutronic experiments were conducted on the plasma core assembly at the Los Alamos National Laboratory to measure selected fundamental nuclear parameters in a gaseous core critical assembly in which a significant fraction (∼20%) of the fissioning took place in gaseous uranium hexafluoride (UF6) fuel; the balance of the fissions occurred in a ring of conventional solid driver fuel rods surrounding the central gaseous core region. Measured parameters included neutron multiplication factors, neutron flux spatial and spectral distributions, reactor decay constants and reactivity worths of both the gaseous UF6 and the solid driver fuel rods for various critical and subcritical configurations. Measured parameters were then compared with theoretically predicted values to determine the adequacy of various analytical neutronics schemes. Theoretical predictions obtained from the various computational schemes for key neutronic parameters were, in general, in good agreement with one another and also with experiment.